Low-phosphorus lubricating oil composition for extended drain intervals

ABSTRACT

The present invention is directed to a lubricating oil composition comprising a major amount of a base oil of lubricating viscosity and a minor amount of each of the following:  
     a) from about 3.0 to about 7.0 weight percent of an ethylene carbonated-treated ashless dispersant;  
     b) from about 2.0 to about 5.0 weight percent of a borated-treated ashless dispersant;  
     c) from about 1.0 to about 3.0 weight percent of a high overbased metal-containing detergent; and  
     d) from about 0.1 to about 2.0 weight percent of a phosphorus-containing compound;  
     wherein the weight percent of total phosphorus in the lubricating oil composition is no more than 0.05 weight percent based on the total weight of the lubricating oil composition.

[0001] This application is a Continuation-in-Part of U.S. applicationSer. No. 10/285,753 filed Oct. 31, 2002.

[0002] The present invention relates to lubricating oil compositionshaving improved wear, extreme pressure, and oxidation performance ininternal combustion engines. In particular, the present inventionrelates to lubricating oil compositions for reducing wear andcontrolling oxidation in internal combustion engines lubricated with alow phosphorus content lubricating oil composition intended for extendeddrain interval applications and to methods employing such.

BACKGROUND OF THE INVENTION

[0003] Current passenger car motor oils meeting the American PetroleumInstitute (API) “SL” or International Lubricant Standardization andApproval Committee (ILSAC) GF-3 specifications are designed forapproximately 5,000 mile (8,000 kilometer) drain intervals or lessdepending on driving severity per Original Equipment Manufacturer (OEM)owner's manuals. These oils pass a rigorous series of industry-standardengine and bench tests documented within the Society of AutomotiveEngineers (SAE) Surface Vehicle Standard J183 (June 2001) and AmericanSociety For Testing and Materials (ASTM) D 4485-01 a (February 2002) todemonstrate, for example, oxidation stability, wear, sludge and varnishdeposit control, among other requirements. However, significantincreases in performance specifications are evolving. Next generationengine oils may soon meet the proposed ILSAC GF-4 specification.

[0004] With the increasing emphasis on oil conservation and the desirefor more maintenance-free vehicles, there is a trend toward extendingengine oil drain intervals. Current API SL quality engine oils providegood engine cleanliness and wear protection at normal drain intervals of3,000 to 10,000 miles. However, problems with excessive oil thickening,increased engine sludge and/or varnish deposits, and engine wear becomeapparent for many SL products as recommended drain intervals areextended.

[0005] Extended oil drains are currently under consideration throughoutthe automotive lubrication industry and were part of early discussionsregarding future engine oil specification requirements (ILSAC GF4).Extension of oil change interval recommendations beyond 15,000 miles isnow being discussed. OEMs are interested in extending the drainintervals on engine oils without compromising the deposit and wearperformance of a lubricating oil composition. Of great importance to oneOEM is protection of the engine during severe operating service, inrental fleets, or during lease periods where the operator has littleincentive to maintain the vehicle properly. For example, one OEM wouldlike engine oil in factory fill and service fill applications that cango at least 30,000 miles before the next engine oil change. This isparticularly desirable in leased vehicles that sometimes go for extendedintervals without an engine oil change at the proper recommended serviceinterval. To provide a lubricating oil composition that meets thisrequirement and the ILSAC GF4 specifications is an extreme challenge.

[0006] The problem of providing an extended service motor oilformulation is a serious one. In essence, an oil must be capable ofproviding satisfactory lubrication for a period of from three to sixtimes as long as had been required in the past. At the same time it mustmaintain the crankcase as well as other parts of the engine free ofharmful sludge deposits, and must afford protection against rust andcorrosion as well as wear protection for engine parts such as valvelifters which are in extreme contact pressure. Moreover, long servicemotor oils must retain the characteristics of suitability forspark-ignition engines such as oxidation stability, viscositymaintenance, cold starting characteristics, certain combustion chambercontrol features, and oil mileage and fuel economy which consumers havecome to expect from all premium grade oils. While additives are knownwhich are capable of increasing one or perhaps two of thesecharacteristics, there are many sources of specific interactions withother lubricant additives that careful and extensive experimentationleads to truly useful motor oil formulations suitable for the moresevere extended service.

[0007] A key requirement in the proposed ILSAC GFA specification is thatthe phosphorus content be reduced from the currently allowable limit of0.10 weight percent specified in the ILSAC GF-3 specification, to as lowas 0.05 weight percent, because phosphorus and its derivatives poisoncatalyst components of catalytic converters. This is a major concern,because effective catalytic converters are needed to reduce pollutionand to meet governmental regulations designed to reduce toxic gases,such as hydrocarbons, carbon monoxide, and nitrogen oxides, in internalcombustion engine exhaust emissions. Such catalytic converters generallyuse a combination of catalytic metals such as platinum or its variationsand metal oxides and are installed in the exhaust streams to convert thetoxic gases to non-toxic gases. When the phosphorus content in theemission is excessive, the components of the catalytic converter becomeineffective and may ultimately lose their intended function.

[0008] One additive class impacted by the new specification is thephosphorus-containing additives used in lubricating oil composition forinternal combustion engines. Zinc dialkyldithiophosphates are, forexample, contained in most of the commercially available internalcombustion engine oils, especially those used for automobiles, becauseof their favorable characteristics as an anti-wear agent and performanceas an oxidation inhibitor. It is generally employed in lubricating oilsat phosphorus levels about 0.1 weight percent when used for wearcontrol. A problem arises when the level of phosphorus is reducedcontaining the phosphorus-containing compound in that there is asignificant reduction in anti-wear and oxidation control performancearising from this diminution in phosphorus content. Therefore, it isnecessary to find a way to reduce phosphorus content while stillretaining the anti-wear and oxidation properties of higher phosphoruscontent engine oils.

[0009] To get more fuel efficiency from engines, even lower viscositylubricants will be required. The only practical way to meet the combinedrequirements for an SAE 0W-20 engine oil is to use synthetic basefluids. Until recently, polyalphaolefin (PAO) base oils combination withester fluids such as C₇-C₉ tetramethanolpropane esters were one way tomeet SAE 0W-20 requirements while maintaining acceptable oil consumptionand oxidation stability. The SAE 0W-20 viscosity grade represents thelowest viscosity grade that will likely be utilized by OEM in factoryfill and service fill applications. This grade of engine oil willtypically be formulated with polyalphaolefin (PAO) base oils becausebase oils derived from crude oil cannot meet the combination ofvolatility and low temperature requirements for this viscosity grade.

[0010] The present invention is directed to a lubricating oilcomposition having extended drain properties as evidenced by improvedwear, extreme pressure, and oxidation performance.

SUMMARY OF THE INVENTION

[0011] The present invention provides a lubricating oil compositionhaving improved wear, extreme pressure, and oxidation performance ininternal combustion engines. More particularly, the present inventionrelates to lubricating oil compositions for reducing wear andcontrolling oxidation in internal combustion engines lubricated with alow phosphorus content lubricating oil composition intended for extendeddrain interval applications and to methods employing such.

[0012] Accordingly, in one of its composition aspects, the presentinvention is directed to a lubricating oil composition comprising amajor amount of a base oil of lubricating viscosity and a minor amountof each of the following:

[0013] a) from about 3.0 to about 7.0 weight percent of an ethylenecarbonated-treated ashless dispersant;

[0014] b) from about 2.0 to about 5.0 weight percent of aborated-treated ashless dispersant;

[0015] c) from about 1.0 to about 3.0 weight percent of a high overbasedmetal-containing detergent; and

[0016] d) from about 0.1 to about 2.0 weight percent of aphosphorus-containing compound;

[0017] wherein the weight percent of total phosphorus in the lubricatingoil composition is no more than 0.05 weight percent based on the totalweight of the lubricating oil composition.

[0018] The lubricating oil composition of the present invention mayfurther comprise a low overbased metal-containing detergent, anitrogen-containing ashless antioxidant, an alkylthiocarbamoyl compound,a molybdenum/nitrogen complex or mixtures thereof.

[0019] Preferably, the base oil of lubricating viscosity employed in thepresent invention is selected from the group consisting of a Group IIIbase stock, Group IV base stock, Group V base stock and any mixturethereof.

[0020] Preferably, the ethylene carbonated-treated and borated-treatedashless dispersant employed in the present invention is selected fromthe group consisting of an alkenyl succinimide, an alkenyl succinicanhydride, an alkenyl succinate ester, benzylamine or mixtures thereof.More preferably, the ashless dispersant is an alkenyl succinimide.

[0021] Preferably, the low overbased and high overbased metal-containingdetergent employable in the present invention is a metal phenate ormetal sulfonate. The metal sulfonate is more preferred.

[0022] Preferably, the phosphorus-containing compound employable in thepresent invention is selected from the group consisting of metaldithiophosphates, phosphorus esters (including phosphates, phosphonates,phosphinates, phosphine oxides, phosphites, phosphonites, phosphinites,phosphines and the like), amine phosphates and amine phosphinates,sulfur-containing phosphorus esters including phosphoro monothionate andphosphoro dithionates, phosphoramides, phosphonamides and the like. Morepreferably, the phosphorus-containing compound is a metaldithiophosphate and, most preferably, a zinc dithiophosphate.

[0023] Preferably, the nitrogen-containing ashless antioxidantemployable in the present invention is an alkylated diphenylamine.

[0024] Preferably, the alkylthiocarbamoyl compound employable in thepresent invention is an alkylene bis(dialkyldithiocarbamate).

[0025] Preferably, the molybdenum/nitrogen complex is amolybdenum/succinimide complex. The complex includes both sulfurized andnon-sulfurized forms. Preferably, the molybdenum/nitrogen complex issulfurized.

[0026] The particularly preferred molybdenum/nitrogen complex isdisclosed in commonly assigned U.S. patent application Ser. No.10/159,446 filed on May 31, 2002 and entitled “REDUCED COLORMOLYBDENUM-CONTAINING COMPOSITION AND A METHOD OF MAKING SAME” whichapplication is incorporated herein by reference in its entirety.

[0027] The present invention is also directed to a method of enhancingthe life of a lubricating oil composition as evidenced by an improvementin wear, extreme pressure, and oxidation performance, the methodcomprising operating an internal combustion engine with a lubricatingoil composition comprising a major amount of a base oil of lubricatingviscosity and a minor amount of each of the following:

[0028] a) from about 3.0 to about 7.0 weight percent of an ethylenecarbonated-treated ashless dispersant;

[0029] b) from about 2.0 to about 5.0 weight percent of aborated-treated ashless dispersant;

[0030] c) from about 1.0 to about 3.0 weight percent of a high overbasedmetal-containing detergent; and

[0031] d) from about 0.1 to about 2.0 weight percent of aphosphorus-containing compound;

[0032] wherein the weight percent of total phosphorus in the lubricatingoil composition is no more than 0.05 weight percent based on the totalweight of the lubricating oil composition.

[0033] Among other factors, the present invention is based on thesurprising discovery that the lubricating oil composition has extendeddrain properties as evidenced by improved wear, extreme pressure, andoxidation performance. The lubricating oil composition of the presentinvention has a low phosphorus content while maintaining excellent wearand oxidation performance that is important in an extended drainlubricating oil.

DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention provides for a low phosphorus lubricatingoil composition having no more than 0.05 weight percent total phosphorusbased on the total weight of the lubricating oil composition. Thecombination of additive components in the lubricating oil composition ofthe present invention provides improved wear, extreme pressure andoxidation performance and are hereinbelow described in detail.

Base Oil of Lubricating Viscosity

[0035] The lubricating oil composition of the present invention includesa major amount of base oil of lubricating viscosity. Base oil as usedherein is defined as a base stock or blend of base stocks which is alubricant component that is produced by a single manufacturer to thesame specifications (independent of feed source or manufacturer'slocation); that meets the same manufacturer's specification; and that isidentified by a unique formula, product identification number, or both.Base stocks may be manufactured using a variety of different processesincluding but not limited to distillation, solvent refining, hydrogenprocessing, oligomerization, esterification, and rerefining. Rerefinedstock shall be substantially free from materials introduced throughmanufacturing, contamination, or previous use. The base oil of thisinvention may be any natural or synthetic lubricating base oil fractionparticularly those having a kinematic viscosity at 100 degreesCentigrade (C) and about 4 centistokes (cSt) to about 20 cSt.Hydrocarbon synthetic oils may include, for example, oils prepared fromthe polymerization of ethylene, i.e., polyalphaolefin or PAO, or fromhydrocarbon synthesis procedures using carbon monoxide and hydrogengases such as in a Fisher-Tropsch process. A preferred base oil is onethat comprises little, if any, heavy fraction; e.g., little, if any;lube oil fraction of viscosity about 20 cSt or higher at about 100degrees C.

[0036] The base oil may be derived from natural lubricating oils,synthetic lubricating oils or mixtures thereof. Suitable base oilincludes base stocks obtained by isomerization of synthetic wax andslack wax, as well as hydrocrackate base stocks produced byhydrocracking (rather than solvent extracting) the aromatic and polarcomponents of the crude. Suitable base oils include those in all APIcategories I, II, III, IV and V as defined in API Publication 1509, 14thEdition, Addendum I, December 1998, which is herein incorporated for allpurposes. Saturates levels and viscosity indices for Group I, II and IIIbase oils are listed in Table 1. Group IV base oils are polyalphaolefins(PAO). Group V base oils include all other base oils not included inGroup I, II, III, or IV. Group II, III and IV base oils are also usefulin the present invention. Group II and III base oils may be prepared bycombining one or more of Group I, II, and III base stocks or base oils.TABLE 1 SATURATES, SULFUR AND VISCOSITY INDEX OF GROUP I, II AND IIIBASE STOCKS Saturates Viscosity Index (As determined by (As determinedby ASTM D 2007) ASTM D 4294, ASTM Sulfur D 4297 or ASTM D Group (Asdetermined by ASTM D 2270) 3120) I Less than 90% saturates and/orGreater than or equal Greater than to 0.03% sulfur to 80 and less than120 II Greater than or equal to 90% saturates Greater than or equal andless than or equal to 0.03% sulfur to 80 and less than 120 III Greaterthan or equal to 90% saturates Greater than or equal and less than orequal to 0.03% sulfur to 120 IV All Polyalphaolefins (PAOs) V All othersnot included in Groups I, II, III, or IV

[0037] Natural lubricating oils may include animal oils, vegetable oils(e.g., rapeseed oils, castor oils and lard oil), petroleum oils, mineraloils, and oils derived from coal or shale.

[0038] Synthetic oils may include hydrocarbon oils and halo-substitutedhydrocarbon oils such as polymerized and inter-polymerized olefins,alkylbenzenes, polyphenyls, alkylated diphenyl ethers, alkylateddiphenyl sulfides, as well as their derivatives, analogues andhomologues thereof, and the like. Synthetic lubricating oils alsoinclude alkylene oxide polymers, interpolymers, copolymers andderivatives thereof wherein the terminal hydroxyl groups have beenmodified by esterification, etherification, etc. Another suitable classof synthetic lubricating oils comprises the esters of dicarboxylic acidswith a variety of alcohols. Esters useful as synthetic oils also includethose made from C₅ to C₁₂ monocarboxylic acids and polyols and polyolethers. Tri-alkyl phosphate ester oils such as those exemplified bytri-n-butyl phosphate and tri-iso-butyl phosphate are also suitable foruse as base oils.

[0039] Silicon-based oils (such as the polyalkyl-, polyaryl-,polyalkoxy-, or polyaryloxy-siloxane oils and silicate oils) compriseanother useful class of synthetic lubricating oils. Other syntheticlubricating oils include liquid esters of phosphorus-containing acids,polymeric tetrahydrofurans, polyalphaolefins, and the like.

[0040] The base oil may be derived from unrefined, refined, rerefinedoils, or mixtures thereof. Unrefined oils are obtained directly from anatural source or synthetic source (e.g., coal, shale, or tar sandbitumen) without further purification or treatment. Examples ofunrefined oils include a shale oil obtained directly from a retortingoperation, a petroleum oil obtained directly from distillation, or anester oil obtained directly from an esterification process, each ofwhich may then be used without further treatment. Refined oils aresimilar to the unrefined oils except that refined oils have been treatedin one or more purification steps to improve one or more properties.Suitable purification techniques include distillation, hydrocracking,hydrotreating, dewaxing, solvent extraction, acid or base extraction,filtration, and percolation, all of which are known to those skilled inthe art. Rerefined oils are obtained by treating used oils in processessimilar to those used to obtain the refined oils. These rerefined oilsare also known as reclaimed or reprocessed oils and often areadditionally processed by techniques for removal of spent additives andoil breakdown products.

[0041] Base oil derived from the hydroisomerization of wax may also beused, either alone or in combination with the aforesaid natural and/orsynthetic base oil. Such wax isomerate oil is produced by thehydroisomerization of natural or synthetic waxes or mixtures thereofover a hydroisomerization catalyst.

[0042] It is preferred to use a major amount of base oil of lubricatingviscosity in the lubricating oil composition of the present invention. Amajor amount of base oil of lubricating viscosity as defined hereincomprises 40 weight percent or more. Preferably about 40 weight percentto about 97 weight percent of at least one of Group III and IV base oil,more preferably about 50 weight percent to about 97 weight percent of atleast one of Group III and IV base oil, still more preferably about 60weight percent to about 97 weight percent of at least one of Group IIIand IV base oil and most preferably about 80 weight percent to about 95weight percent of at least one of Group III and IV base oil in thelubricating oil composition including up to about 10 weight percent of aGroup V base oil may be added. (When weight percent is used herein, itis referring to weight percent of the lubricating oil composition unlessotherwise specified.)

Ashless Dispersant

[0043] The dispersant employed in the lubricating oil composition of thepresent invention is an ashless dispersant such as an alkenylsuccinimide, an alkenyl succinic anhydride, an alkenyl succinate ester,and the like, or mixtures of such dispersants.

[0044] Ashless dispersants are broadly divided into several groups. Onesuch group is directed to copolymers which contain a carboxylate esterwith one or more additional polar function, including amine, amide,imine, imide, hydroxyl carboxyl, and the like. These products can beprepared by copolymerization of long chain alkyl acrylates ormethacrylates with monomers of the above function. Such groups includealkyl methacrylate-vinyl pyrrolidinone copolymers, alkylmethacrylate-dialkylaminoethyl methacrylate copolymers and the like.Additionally, high molecular weight amides and polyamides or esters andpolyesters such as tetraethylene pentamine, polyvinyl polysterarates andother polystearamides may be employed. Preferred ashless dispersants arealkenyl succinimides and more preferably N-substituted long chainalkenyl succinimides.

[0045] Alkenyl succinimides are usually derived from the reaction ofalkenyl succinic acid or anhydride and alkylene polyamines. Thesecompounds are generally considered to have the formula:

[0046] wherein R¹ is a substantially hydrocarbon radical having amolecular weight from about 400 to about 3,000, that is, R¹ is ahydrocarbyl radical, preferably an alkenyl radical, containing about 30to about 200 carbon atoms; Alk is an alkylene radical of about 2 toabout 10, preferably about 2 to about 6, carbon atoms, R², R³, and R⁴are selected from a C₁ to C₄ alkyl or alkoxy or hydrogen, preferablyhydrogen, and a is an integer from 0 to about 10, preferably 0 to about3. The actual reaction product of alkylene succinic acid or anhydrideand alkylene polyamine will comprise the mixture of compounds includingsuccinamic acids and succinimides. However, it is customary to designatethis reaction product as a succinimide of the described formula, sincethis will be a principal component of the mixture. See, for example,U.S. Pat. Nos. 3,202,678; 3,024,237; and 3,172,892.

[0047] The N-substituted alkenyl succinimides can be prepared byreacting maleic anhydride with an olefinic hydrocarbon followed byreacting the resulting alkenyl succinic anhydride with the alkylenepolyamine. The R¹ radical of the above formula, that is, the alkenylradical, is preferably derived from a polymer prepared from an olefinmonomer containing from about 2 to about 5 carbon atoms. Thus, thealkenyl radical is obtained by polymerizing an olefin containing fromabout 2 to about 5 carbon atoms to form a hydrocarbon having a molecularweight ranging from about 400 to about 3,000. Such olefin monomers areexemplified by ethylene, propylene, 1-butene, 2-butene, isobutene, andmixtures thereof.

[0048] The preferred alkylene polyamines used to prepare thesuccinimides are of the formula:

[0049] wherein b is an integer of from 0 to about 10 and Alk, R², R³,and R⁴ are as defined above.

[0050] The alkylene amines include principally methylene amines,ethylene amines, butylene amines, propylene amines, pentylene amines,hexylene amines, heptylene amines, octylene amines, other polymethyleneamines and also the cyclic and the higher homologs of such amines aspiperazine and amino alkyl-substituted piperazines. They are exemplifiedspecifically by ethylene diamine, triethylene tetraamine, propylenediamine, decamethyl diamine, octamethylene diamine, diheptamethylenetriamine, tripropylene tetraamine, tetraethylene pentamine, trimethylenediamine, pentaethylene hexamine, ditrimethylene triamine,2-heptyl-3-(2-aminopropyl)-imidazoline, 4-methyl imidazoline,N,N-dimethyl-1,3-propane diamine, 1,3-bis(2-aminoethyl)imidazoline,1-(2-aminopropyl)-piperazine, 1,4-bis(2-aminoethyl)piperazine and2-methyl-1-(2-aminobutyl)piperazine. Higher homologs such as areobtained by condensing two or more of the above-illustrated alkyleneamines likewise are useful.

[0051] The ethylene amines are especially useful. They are described insome detail under the heading “Ethylene Amines” in Encyclopedia ofChemical Technology, Kirk-Othmer, Vol. 5, pp. 898-905 (IntersciencePublishers, New York, 1950).

[0052] The term “ethylene amine” is used in a generic sense to denote aclass of polyamines conforming for the most part to the structure:

H₂N(CH₂CH₂NH)_(c)H

[0053] wherein c is an integer from 1 to about 10.

[0054] Thus, it includes, for example, ethylene diamine, diethylenetriamine, triethylene tetraamine, tetraethylene pentamine, pentaethylenehexamine, and the like.

[0055] Also included within the term “alkenyl succinimides” arepost-treated succinimides such as post-treatment processes involvingethylene carbonate and boric acid disclosed by Wollenberg, et al., U.S.Pat. No. 4,612,132; Wollenberg, et al., U.S. Pat. No. 4,746,446; and thelike as well as other post-treatment processes each of which areincorporated herein by reference in its entirety.

[0056] In the lubricating oil composition of the present invention boththe ethylene carbonate-treated and boric acid-treated succinimides areemployed. The ethylene carbonate-treated ashless dispersant and theborated ashless dispersant are preferably contained in the lubricatingoil composition in a total amount of from about 5.0 to about 12 weightpercent, preferably from about 6.5 to about 9.5 weight percent, morepreferably from about 7.5 to about 9.0 weight percent, based on thetotal weight of the lubricating oil composition. The weight range of theethylene carbonated-treated ashless dispersant will be from about 3.0 toabout 7.0 weight percent, preferably from about 4.0 to about 6.0 weightpercent, more preferably from about 4.5 to about 5.5 weight percent.

[0057] The weight range of the borated-treated ashless dispersant willbe from about 2.0 to about 5.0 weight percent, preferably from about 2.5to about 3.5 weight percent, more preferably from about 3.0 to about 3.5weight percent.

[0058] The combination of the two succinimides produces superiordetergency and soot dispersancy to either the carbonated-treated orborated-treated succinimides when used alone.

Metal-Containing Detergent

[0059] The detergent employed in the lubricating oil composition of thepresent invention is a metal-containing detergent. There are a number ofmaterials that are suitable as detergents for the purpose of thisinvention. These materials include phenates (high overbased or lowoverbased), high overbased phenate stearates, phenolates, salicylates,phosphonates, thiophosphonates and sulfonates and mixtures thereof.Preferably, sulfonates are used, such as high overbased sulfonates, lowoverbased sulfonates, or phenoxy sulfonates. In addition the sulfonicacids themselves can also be used.

[0060] The sulfonate detergent is preferably an alkali or alkaline earthmetal salt of a hydrocarbyl sulfonic acid having from about 15 to about200 carbons. Preferably the term “sulfonate” encompasses the salts ofsulfonic acid derived from petroleum products. Such acids are well knownin the art. They can be obtained by treating petroleum products withsulfuric acid or sulfur trioxide. The acids thus obtained are known aspetroleum sulfonic acids and the salts as petroleum sulfonates. Most ofthe petroleum products which become sulfonated contain anoil-solubilizing hydrocarbon group. Also included within the meaning of“sulfonate” are the salts of sulfonic acids of synthetic alkylarylcompounds. These acids also are prepared by treating an alkylarylcompound with sulfuric acid or sulfur trioxide. At least one alkylsubstituent of the aryl ring is an oil-solubilizing group, as discussedabove. The acids thus obtained are known as alkylaryl sulfonic acids andthe salts as alkylaryl sulfonates. The sulfonates where the alkyl isstraight-chain are the well-known linear alkylaryl sulfonates.

[0061] The acids obtained by sulfonation are converted to the metalsalts by neutralizing with a basic reacting alkali or alkaline earthmetal compound to yield the Group I or Group II metal sulfonates.Generally, the acids are neutralized with an alkali metal base. Alkalineearth metal salts are obtained from the alkali metal salt by metathesis.Alternatively, the sulfonic acids can be neutralized directly with analkaline earth metal base. The sulfonates can then be overbased. Forpurposes of the present invention, overbasing is preferred. Overbasedmaterials and methods of preparing such materials are well known tothose skilled in the art. See, for example, LeSuer U.S. Pat. No.3,496,105, issued Feb. 17, 1970, particularly columns 3 and 4.

[0062] The sulfonates are present in the oil dispersion in the form ofalkali and/or alkaline earth metal salts, or mixtures thereof. Thealkali metals include lithium, sodium and potassium. The alkaline earthmetals include barium magnesium and calcium, of which the latter two arepreferred.

[0063] Particularly preferred, however, because of their wideavailability, are salts of the petroleum sulfonic acids, particularlythe petroleum sulfonic acids which are obtained by sulfonating varioushydrocarbon fractions such as lubricating oil fractions and extractsrich in aromatics which are obtained by extracting a hydrocarbon oilwith a selective solvent, which extracts may, if desired, be alkylatedbefore sulfonation by reacting them with olefins or alkyl chlorides bymeans of an alkylation catalyst; organic polysulfonic acids such asbenzene disulfonic acid which may or may not be alkylated; and the like.

[0064] The preferred salts for use in the present invention are those ofalkylated aromatic sulfonic acids in which the alkyl radical or radicalscontain at least about 8 carbon atoms, for example from about 8 to about22 carbon atoms. Another preferred group of sulfonate starting materialsare the aliphatic-substituted cyclic sulfonic acids in which thealiphatic substituents or substituents contain a total of at least about12 carbon atoms, such as the alkyl aryl sulfonic acids, alkylcycloaliphatic sulfonic acids, the alkyl heterocyclic sulfonic acids andaliphatic sulfonic acids in which the aliphatic radical or radicalscontain a total of at least about 12 carbon atoms. Specific examples ofthese oil-soluble sulfonic acids include petroleum sulfonic acids, mono-and poly-wax-substituted naphthalene sulfonic acids, substitutedsulfonic acids, such as cetyl benzene sulfonic acids, cetyl phenylsulfonic acids, and the like, aliphatic sulfonic acid, such as paraffinwax sulfonic acids, hydroxy-substituted paraffin wax sulfonic acids,etc., cycloaliphatic sulfonic acids, petroleum naphthalene sulfonicacids, cetyl cyclopentyl sulfonic acid, mono- and poly-wax-substitutedcyclohexyl sulfonic acids, and the like. The term “petroleum sulfonicacids” is intended to cover all sulfonic acids that are derived directlyfrom petroleum products.

[0065] Typical Group II metal sulfonates suitable for use in the presentinvention include the metal sulfonates exemplified as follows: calciumwhite oil benzene sulfonate, barium white oil benzene sulfonate,magnesium white oil benzene sulfonate, calcium dipolypropene benzenesulfonate, barium dipolypropene benzene sulfonate, magnesiumdipolypropene benzene sulfonate, calcium mahogany petroleum sulfonate,barium mahogany petroleum sulfonate, magnesium mahogany petroleumsulfonate, calcium triacontyl sulfonate, magnesium triacontyl sulfonate,calcium lauryl sulfonate, barium lauryl sulfonate, magnesium laurylsulfonate, etc.

[0066] The lubricating oil composition of the present invention mayemploy a high overbased and low overbased metal-containing detergent,i.e., metal sulfonate. The high overbased metal-containing detergentwill generally range from about 1.0 to about 3.0 weight percent andpreferably from about 1.4 to about 1.8 weight percent, based on thetotal weight of the lubricating oil composition and has a Total BaseNumber (TBN) from about 5.7 to about 7.4. The low overbasedmetal-containing detergent will generally range from about 0.2 to about6.0 weight percent and preferably from about 0.3 to about 0.5 weightpercent, based on the total weight of the lubricating oil compositionand has a TBN from about 0.5 to about 0.9.

Phosphorus-Containing Compound

[0067] The phosphorus-containing compound employed in the lubricatingoil composition of the present invention is selected from the groupconsisting of metal dithiophosphates, phosphorus esters (includingphosphates, phosphonates, phosphinates, phosphine oxides, phosphites,phosphonites, phosphinites, phosphines and the like), amine phosphatesand amine phosphinates, sulfur-containing phosphorus esters includingphosphoro monothionate and phosphoro dithionates, phosphoramides,phosphonamides and the like; all of which are well known in the art.Preferably, the phosphorus-containing compound is a metaldithiophosphate and, more preferably, a zinc dithiophosphate. Still morepreferably, the phosphorous containing compound is a zincdialkyldithiophosphate wherein the alkyl groups are independentlyselected form C₃ to C₁₃, branched or straight chain carbon groupsincluding mixtures thereof. Most preferably, the phosphorus containingcompound is a zinc dialkyldithiophosphate made from a mixture ofsecondary alcohols where the average carbon chain length is betweenabout 3 and about 6 carbon atoms.

[0068] The metal dithiophosphates are characterized by formula I:

[0069] wherein each R⁵ is independently a hydrocarbyl group containingfrom about 3 to about 13 carbon atoms, M is a metal, and d is an integerequal to the valence of M.

[0070] The hydrocarbyl groups, R⁵, in the dithiophosphate (or asdescribed elsewhere in this application) can be a C₃ to C₁₃ alkyl, C₃ toC₁₃ cycloalkyl, C₇ to C₁₃ aralkyl or C₇ to C₁₃ alkaryl groups, or asubstantially hydrocarbon group of similar structure. By “substantiallyhydrocarbon” is meant hydrocarbons that contain substituent groups suchas ether, ester, nitro, or halogen which do not materially affect thehydrocarbon character of the group.

[0071] Illustrative alkyl groups include isopropyl, isobutyl, n-butyl,sec-butyl, the various amyl groups, n-hexyl, methylisobutyl carbinyl,heptyl, 2-ethylhexyl, diisobutyl, isooctyl, nonyl, behenyl, decyl,dodecyl, tridecyl, etc. Illustrative lower alkylphenyl groups includebutylphenyl, amylphenyl, heptylphenyl, etc. Cycloalkyl groups likewiseare useful and these include chiefly cyclohexyl and the loweralkyl-cyclohexyl radicals. Many substituted hydrocarbon groups may alsobe used, e.g., chlorophenyl, dichlorophenyl, and dichlorodecyl. Inanother embodiment, at least one R⁵ group is an isopropyl or secondarybutyl group. In yet another embodiment, both R⁵ groups are secondaryalkyl groups.

[0072] The phosphorodithioic acids from which the metal salts useful inthe present invention are prepared are well known. Examples ofdihydrocarbyl phosphorodithioic acids and metal salts, and processes forpreparing such acids and salts are found in, for example, U.S. Pat. Nos.4,263,150; 4,289,635; 4,308,154; and 4,417,990, which are herebyincorporated by reference for such disclosures.

[0073] The phosphorodithioic acids are typically prepared by thereaction of phosphorus pentasulfide with an alcohol or phenol ormixtures of alcohols and/or phenols. The reaction involves four moles ofthe alcohol or phenol per mole of phosphorus pentasulfide, and may becarried out within the temperature range from about 50° C. to about 200°C. Thus, the preparation of O,O-di-n-hexyl phosphorodithioic acidinvolves the reaction of phosphorus pentasulfide with four moles ofn-hexyl alcohol at about 100° C. for about two hours. Hydrogen sulfideis liberated and the residue is the defined acid. The preparation of themetal salt of this acid may be effected by reaction with metal oxide.Simply mixing and heating these two reactants is sufficient to cause thereaction to take place and the resulting product is sufficiently purefor the purposes of this invention.

[0074] The metal dihydrocarbyl dithiophosphates that are useful in thisinvention include those salts containing Group I metals, Group IImetals, zinc, aluminum, lead, tin, molybdenum, manganese, cobalt, andnickel or mixtures thereof. The Group II metals, zinc, aluminum, tin,iron, cobalt, lead, molybdenum, manganese, nickel and copper are amongthe preferred metals. Zinc and copper either alone or in combination areespecially useful metals. Especially preferred is zinc. In oneembodiment, the lubricating oil compositions of the present inventioncontain examples of metal compounds which may be reacted with the acidinclude lithium oxide, lithium hydroxide, sodium hydroxide, sodiumcarbonate, potassium hydroxide, potassium carbonate, silver oxide,magnesium oxide, magnesium hydroxide, calcium oxide, zinc hydroxide,zinc oxide, strontium hydroxide, cadmium oxide, cadmium hydroxide,barium oxide, aluminum oxide, iron carbonate, copper hydroxide, leadhydroxide, tin burylate, cobalt hydroxide, nickel hydroxide, nickelcarbonate, etc.

[0075] In some instances, the incorporation of certain ingredients suchas small amounts of the metal acetate or acetic acid (glacial) inconjunction with the metal reactant will facilitate the reaction andresult in an improved product. For example, the use of up to about 5% ofzinc acetate in combination with the required amount of zinc oxidefacilitates the formation of a zinc phosphorodithioate.

[0076] In one preferred embodiment, the alkyl groups, R⁵, are derivedfrom secondary alcohols such as isopropyl alcohol, secondary butylalcohol, 2-pentanol, 4-methyl-2-pentanol, 2-hexanol, 3-hexanol, etc.Preferably R⁵ is derived from a mixture of secondary alcohols such as2-butanol and 4-methyl-2-pentanol. Particularly preferred R⁵ is derivedfrom the above mixture containing from about 65 to about 75 weightpercent 2-butanol with the remainder 4-methyl-2-pentanol.

[0077] Especially useful metal phosphorodithioates can be prepared fromphosphorodithioic acids that, in turn, are prepared by the reaction ofphosphorus pentasulfide with mixtures of alcohols. In addition, the useof such mixtures enables the utilization of cheaper alcohols which inthemselves may not yield oil-soluble phosphorodithioic acids.

[0078] Useful mixtures of metal salts of dihydrocarbyl dithiophosphoricacid are obtained by reacting phosphorus pentasulfide with a mixture of(a) isopropyl or secondary butyl alcohol, and (b) an alcohol containingat least about 5 carbon atoms wherein at least about 10 mole percent,preferably about 20 or about 25 mole percent, of the alcohol in themixture is isopropyl alcohol, secondary butyl alcohol or a mixturethereof.

[0079] Thus, a mixture of isopropyl and hexyl alcohols can be used toproduce a very effective, oil-soluble metal phosphorodithioate. For thesame reason, mixtures of phosphorodithoic acids can be reacted with themetal compounds to form less expensive, oil-soluble salts.

[0080] The mixtures of alcohols may be mixtures of different primaryalcohols, mixtures of different secondary alcohols or mixtures ofprimary and secondary alcohols. Examples of useful mixtures include:n-butanol and n-octanol; n-pentanol and 2-ethyl-1-hexanol; isobutanoland n-hexanol; isobutanol and isoamyl alcohol; isopropanol and4-methyl-2-pentanol; isopropanol and sec-butyl alcohol; isopropanol andisooctyl alcohol; sec-butyl alcohol and 4-methyl-2-pentanol, etc.Particularly useful alcohol mixtures are mixtures of secondary alcoholscontaining at least about 20 mole percent and preferably at least about40 mole percent of isopropyl alcohol. In a preferred embodiment, atleast about 75 mole percent of sec-butyl alcohol is used and preferablycombined with 4-methyl-2-pentanol, and most preferably further combinedwith a zinc metal.

[0081] Particularly preferred metal dihydrocarbyl phosphorodithioatesinclude the zinc dithiophosphates. Patents describing the synthesis ofsuch zinc dithio-phosphates include U.S. Pat. Nos. 2,680,123; 3,000,822;3,151,075; 3,385,791; 4,377,527; 4,495,075 and 4,778,906, which areincorporated herein by reference in their entirety.

[0082] The amount of the phosphorus-containing compound in thelubricating oil composition of the present invention will range fromabout 0.1 to about 0.7 weight percent which, at these levels, the weightpercent of phosphorus is from about 0.01 to about 0.05 weight percentbased on the total weight of the lubricating oil composition.

Nitrogen-Containing Ashless Antioxidant

[0083] The nitrogen-containing ashless antioxidants of the presentinvention are the diphenylamine type. Examples of diphenylamine-typeantioxidants include, but are not limited to, alkylated diphenylamine,phenyl-α-naphthylamine, and alkylated-α-naphthylamine. Preferably, thenitrogen-containing ashless antioxidant is an alkylated diphenylaminesuch as, for example, dialkylated diphenylamine. The nitrogen-containingashless antioxidant is generally incorporated into the lubricating oilcomposition of the present invention in an amount of about 0.5 to about3.0 weight percent, preferably about 1.0 to about 2.0 weight percent,based on the total weight of the lubricating oil composition.

Alkylthiocarbamoyl Compound

[0084] The alkylthiocarbamoyl compound of the lubricating oilcomposition of the present invention may be represented by the formula:

[0085] wherein R⁶, R⁷, R⁸ and R⁹ are the same or different and eachrepresents an alkyl group of 1 to about 18 carbon atoms, and (X)represents S, S—S, S—CH₂—S, S—CH₂—CH₂—S, S—CH₂—CH₂—CH₂—S orS—CH₂—CH(CH₃)—CH₂—S. Preferably, R⁶, R⁷, R⁸, and R⁹ are independentlyselected from alkyl groups having 1 to about 6 carbon atoms. Morepreferably, the dithiocarbamate compound is methylenebis(dibutyldithiocarbamate).

[0086] The lubricating oil composition of the present invention willgenerally have from about 0.3 to about 1.0 weight percent, preferablyabout 0.3 to about 0.7 weight percent, most preferably about 0.4 toabout 0.6 weight percent, of the alkylthiocarbamoyl compound, based onthe total weight of the lubricating oil composition.

Molybdenum/Nitrogen Complex

[0087] The molybdenum/nitrogen complex employed in the lubricating oilcomposition of the present invention may be generally characterized as amolybdenum complex of a basic nitrogen compound. Such complexes areknown in the art and are described, for example, in U.S. Pat. No.4,263,152 to King et al., the disclosure of which is hereby incorporatedby reference.

[0088] The structure of the molybdenum/nitrogen complex employed in thelubricating oil composition of the present invention are not known withcertainty; however, they are believed to be compounds in whichmolybdenum, whose valences are satisfied with atoms of oxygen or sulfur,is either complexed by, or the salt of, one or more nitrogen atoms ofthe basic nitrogen containing compound used in the preparation of thesecompositions.

[0089] The molybdenum compounds used to prepare the molybdenum andmolybdenum/nitrogen complexes employed in this invention are acidicmolybdenum compounds. By acidic is meant that the molybdenum compoundswill react with a basic nitrogen compound as measured by ASTM test D-664or D-2896 titration procedure. Typically these molybdenum compounds arehexavalent and are represented by the following compositions: molybdicacid, ammonium molybdate, sodium molybdate, potassium molybdate andother alkaline metal molybdates and other molybdenum salts such ashydrogen salts, e.g., hydrogen sodium molybdate, MoOCl₄, MoO₂Br₂,Mo₂O₃Cl₆, molybdenum trioxide or similar acidic molybdenum compounds.Preferred acidic molybdenum compounds are molybdic acid, ammoniummolybdate, and alkali metal molybdates. Particularly preferred aremolybdic acid and ammonium molybdate.

[0090] The basic nitrogen-containing compound used to prepare themolybdenum/nitrogen complexes have at least one basic nitrogen and arepreferably oil-soluble. Typical examples are succinimides, carboxylicacid amides, hydrocarbyl monoamines, hydrocarbon polyamines, Mannichbases, phosphoramides, thiophosphoramides, phosphonamides, dispersantviscosity index improvers, and mixtures thereof. Any of thenitrogen-containing compounds may be after-treated with, e.g., boron,using procedures well known in the art so long as the compositionscontinue to contain basic nitrogen. These after-treatments areparticularly applicable to succinimides and Mannich base compositions.

[0091] The succinimides that can be used to prepare the molybdenumcomplexes described herein are disclosed in numerous references and arewell known in the art. Certain fundamental types of succinimides and therelated materials encompassed by the term of art “succinimide” aretaught in U.S. Pat. Nos. 3,219,666; 3,172,892; and 3,272,746, thedisclosures of which are hereby incorporated by reference. The term“succinimide” is understood in the art to include many of the amide,imide, and amidine species which may also be formed. The predominantproduct however is a succinimide and this term has been generallyaccepted as meaning the product of a reaction of an alkenyl substitutedsuccinic acid or anhydride with a nitrogen-containing compound.Preferred succinimides, because of their commercial availability, arethose succinimides prepared from a hydrocarbyl succinic anhydride,wherein the hydrocarbyl group contains from about 24 to about 350 carbonatoms, and an ethylene amine. Ethylene amines are especiallycharacterized by ethylene diamine, diethylene triamine, triethylenetetramine, and tetraethylene pentamine. Particularly preferred are thosesuccinimides prepared from polyisobutenyl succinic anhydride of about 70to about 128 carbon atoms and tetraethylene pentamine or triethylenetetramine or mixtures thereof.

[0092] Also included within the term “succinimide” are the cooligomersof a hydrocarbyl succinic acid or anhydride and a poly secondary aminecontaining at least one tertiary amino nitrogen in addition to two ormore secondary amino groups. Ordinarily this composition has betweenabout 1,500 and about 50,000 average molecular weight. A typicalcompound would be that prepared by reacting polyisobutenyl succinicanhydride and ethylene dipiperazine.

[0093] Carboxylic acid amide compounds are also suitable startingmaterials for preparing the molybdenum complexes employed in the presentinvention. Typical of such compounds are those disclosed in U.S. Pat.No. 3,405,064, the disclosure of which is hereby incorporated byreference. These compounds are ordinarily prepared by reacting acarboxylic acid or anhydride or ester thereof, having at least about 12to about 350 aliphatic carbon atoms in the principal aliphatic chainand, if desired, having sufficient pendant aliphatic groups to renderthe molecule oil soluble with an amine or a hydrocarbyl polyamine, suchas an ethylene amine, to give a mono or polycarboxylic acid amide.Preferred are those amides prepared from (1) a carboxylic acid of theformula R¹⁰COOH, where R¹⁰ is C₁₂ to C₂₀ alkyl or a mixture of this acidwith a polyisobutenyl carboxylic acid in which the polyisobutenyl groupcontains from about 72 to about 128 carbon atoms and (2) an ethyleneamine, especially triethylene tetramine or tetraethylene pentamine ormixtures thereof.

[0094] Another class of basic nitrogen-compounds which are useful inpreparing the molybdenum/nitrogen complex employed in the presentinvention are hydrocarbyl monoamines and hydrocarbyl polyamines,preferably of the type disclosed in U.S. Pat. No. 3,574,576, thedisclosure of which is hereby incorporated by reference. The hydrocarbylgroup, which is preferably alkyl, or olefinic having one or two sites ofunsaturation, usually contains from about 9 to about 350 carbon atoms,preferably from about 20 to about 200 carbon atoms. Particularlypreferred hydrocarbyl polyamines are those which are derived, e.g., byreacting polyisobutenyl chloride and a polyalkylene polyamine, such asan ethylene amine, e.g., ethylene diamine, diethylene triamine,tetraethylene pentamine, 2-aminoethylpiperazine, 1,3-propylene diamine,1,2-propylenediamine, and the like.

[0095] Another class of basic nitrogen-compounds useful for supplyingbasic nitrogen is the Mannich base compositions. These compounds areprepared from a phenol or C₉ to C₂₀₀ alkylphenol, an aldehyde, such asformaldehyde or formaldehyde precursor such as paraformaldehyde, and anamine compound. The amine may be a mono or polyamine and typicalcompositions are prepared from an alkylamine, such as methylamine or anethylene amine, such as, diethylene triamine, or tetraethylenepentamine, and the like. The phenolic material may be sulfurized andpreferably is dodecylphenol or a C₈₀ to C₁₀₀ alkylphenol. TypicalMannich bases which can be used in this invention are disclosed in U.S.Pat. Nos. 4,157,309 and 3,649,229; 3,368,972; and 3,539,663, thedisclosures of which are hereby incorporated by reference. The lastreferenced discloses Mannich bases prepared by reacting an alkylphenolhaving at least about 50 carbon atoms, preferably about 50 to about 200carbon atoms with formaldehyde and an alkylene polyamine HN(ANH)_(e)Hwhere A is a saturated divalent alkyl hydrocarbon of about 2 to about 6carbon atoms and e is 1 to about 10 and where the condensation productof said alkylene polyamine may be further reacted with urea or thiourea.The utility of these Mannich bases as starting materials for preparinglubricating oil additives can often be significantly improved bytreating the Mannich base using conventional techniques to introduceboron into the compound.

[0096] Another class of basic nitrogen-containing compounds useful forpreparing the molybdenum complexes employed in the present invention arethe phosphoramides and phosphonamides such as those disclosed in U.S.Pat. Nos. 3,909,430 and 3,968,157, the disclosures of which are herebyincorporated by reference. These compounds may be prepared by forming aphosphorus compound having at least one P—N bond. They can be prepared,for example, by reacting phosphorus oxychloride with a hydrocarbyl diolin the presence of a monoamine or by reacting phosphorus oxychloridewith a difunctional secondary amine and a mono-functional amine.Thiophosphoramides can be prepared by reacting an unsaturatedhydrocarbon compound containing from about 2 to about 450 or more carbonatoms, such as polyethylene, polyisobutylene, polypropylene, ethylene,1-hexene, 1,3-hexadiene, isobutylene, 4-methyl-1-pentene, and the like,with phosphorus pentasulfide and a nitrogen-containing compound asdefined above, particularly an alkylamine, alkyldiamine, alkylpolyamine,or an alkyleneamine, such as ethylene diamine, diethylenetriamine,triethylenetetramine, tetraethylenepentamine, and the like.

[0097] Another class of basic nitrogen-containing compounds useful inpreparing the molybdenum complexes employed in the present inventionincludes the so-called dispersant viscosity index improvers (VIimprovers). These VI improvers are commonly prepared by functionalizinga hydrocarbon polymer, especially a polymer derived from ethylene and/orpropylene, optionally containing additional units derived from one ormore co-monomers such as alicyclic or aliphatic olefins or diolefins.The functionalization may be carried out by a variety of processes whichintroduce a reactive site or sites which usually has at least one oxygenatom on the polymer. The polymer is then contacted with anitrogen-containing source to introduce nitrogen-containing functionalgroups on the polymer backbone. Commonly used nitrogen sources includeany basic nitrogen compound especially those nitrogen-containingcompounds and compositions described herein. Preferred nitrogen sourcesare alkylene amines, such as ethylene amines, alkyl amines, and Mannichbases.

[0098] Preferred basic nitrogen-containing compounds for preparing themolybdenum/nitrogen complex employed in the present invention aresuccinimides, carboxylic acid amides, and Mannich bases. More preferredare succinimides having an average molecular weight of about 1,000 orabout 1,300 or about 2,300 and mixtures thereof. Such succinimides canbe post treated with boron or ethylene carbonate as known in the art.

[0099] Preferably, the molybdenum/nitrogen complexes of the presentinvention is sulfurized. Representative sulfur sources for preparing themolybdenum/sulfur complexes used in this invention are sulfur, hydrogensulfide, sulfur monochloride, sulfur dichloride, phosphoruspentasulfide, R¹¹S_(f) where R¹¹ is hydrocarbyl, preferably C₁ to C₄₀alkyl, and f is at least 2, inorganic sulfides and polysulfides such as(NH₄)₂S_(g), where g is at least 1, thioacetamide, thiourea, andmercaptans of the formula R¹¹SH where R¹¹ is as defined above. Alsouseful as sulfurizing agents are traditional sulfur-containingantioxidants such as wax sulfides and polysulfides, sulfurized olefins,sulfurized carboxylic and esters and sulfurized ester-olefins, andsulfurized alkylphenols and the metal salts thereof.

[0100] The sulfurized fatty acid esters are prepared by reacting sulfur,sulfur monochloride, and/or sulfur dichloride with an unsaturated fattyester under elevated temperatures. Typical esters include C₁ to C₂₀alkyl esters of C₈ to C₂₄ unsaturated fatty acids, such as palmitoleic,oleic, ricinoleic, petroselinic, vaccenic, linoleic, linolenic,oleostearic, licanic, paranaric, tariric, gadoleic, arachidonic,cetoleic, etc. Particularly good results have been obtained with mixedunsaturated fatty acid esters, such as are obtained from animal fats andvegetable oils, such as tall oil, linseed oil, olive oil, caster oil,peanut oil, rape oil, fish oil, sperm oil, and so forth.

[0101] Exemplary fatty esters include lauryl tallate, methyl oleate,ethyl oleate, lauryl oleate, cetyl oleate, cetyl linoleate, laurylricinoleate, oleyl linoleate, oleyl stearate, and alkyl glycerides.

[0102] Cross-sulfurized ester olefins, such as a sulfurized mixture ofC₁₀ to C₂₅ olefins with fatty acid esters of C₁₀ to C₂₅ fatty acids andC₁₀ to C₂₅ alkyl or alkenyl alcohols, wherein the fatty acid and/or thealcohol is unsaturated may also be used.

[0103] Sulfurized olefins are prepared by the reaction of the C₃ to C₆olefin or a low-molecular-weight polyolefin derived therefrom with asulfur-containing compound such as sulfur, sulfur monochloride, and/orsulfur dichloride.

[0104] Also useful are the aromatic and alkyl sulfides, such as dibenzylsulfide, dixylyl sulfide, dicetyl sulfide, diparaffin wax sulfide andpolysulfide, cracked wax-olefin sulfides and so forth. They can beprepared by treating the starting material, e.g., olefinicallyunsaturated compounds, with sulfur, sulfur monochloride, and sulfurdichloride. Particularly preferred are the paraffin wax thiomersdescribed in U.S. Pat. No. 2,346,156.

[0105] Sulfurized alkyl phenols and the metal salts thereof includecompounds such as sulfurized dodecylphenol and the calcium saltsthereof. The alkyl group ordinarily contains from about 9 to about 300carbon atoms. The metal salt may be preferably, a Group I or Group IIsalt, especially sodium, calcium, magnesium, or barium.

[0106] Preferred sulfur sources are sulfur, hydrogen sulfide, phosphoruspentasulfide, R¹²S_(h) where R¹² is hydrocarbyl, preferably C₁ to C₁₀alkyl, and h is at least about 3, mercaptans wherein R¹² is C₁ to C₁₀alkyl, inorganic sulfides and polysulfides, thioacetamide, and thiourea.Most preferred sulfur sources are sulfur, hydrogen sulfide, phosphoruspentasulfide, and inorganic sulfides and polysulfides.

[0107] The polar promoter used in the preparation of themolybdenum/nitrogen complex employed in this invention is one whichfacilitates the interaction between the acidic molybdenum compound andthe basic nitrogen-containing compound. A wide variety of such promotersare well known to those skilled in the art. Typical promoters are1,3-propanediol, 1,4-butane-diol, diethylene glycol, butyl cellosolve,propylene glycol, 1,4-butyleneglycol, methyl carbitol, ethanolamine,diethanolamine, N-methyl-diethanol-amine, dimethyl formamide, N-methylacetamide, dimethyl acetamide, methanol, ethylene glycol, dimethylsulfoxide, hexamethyl phosphoramide, tetrahydrofuran and water.Preferred are water and ethylene glycol. Particularly preferred iswater.

[0108] While ordinarily the polar promoter is separately added to thereaction mixture, it may also be present, particularly in the case ofwater, as a component of non-anhydrous starting materials or as watersof hydration in the acidic molybdenum compound, such as(NH₄)₆Mo₇O₂₄.H₂O. Water may also be added as ammonium hydroxide.

[0109] A method for preparing the molybdenum/nitrogen complex used inthe present invention is to prepare a solution of the acidic molybdenumprecursor and a polar promoter with a basic nitrogen-containing compoundwith or without diluent. The diluent is used, if necessary, to provide asuitable viscosity for easy stirring. Typical diluents are lubricatingoil and liquid compounds containing only carbon and hydrogen. Ifdesired, ammonium hydroxide may also be added to the reaction mixture toprovide a solution of ammonium molybdate. This reaction is carried outat a variety of temperatures, typically at or below the melting point ofthe mixture to reflux temperature. It is ordinarily carried out atatmospheric pressure although higher or lower pressures may be used ifdesired. This reaction mixture may optionally be treated with a sulfursource as defined above at a suitable pressure and temperature for thesulfur source to react with the acidic molybdenum and basicnitrogen-containing compounds. In some cases, removal of water from thereaction mixture may be desirable prior to completion of reaction withthe sulfur source.

[0110] In a preferred and improved method for preparing themolybdenum/nitrogen complex, the reactor is agitated and heated at atemperature less than or equal to about 120 degrees Celsius, preferablyfrom about 70 degrees Celsius to about 90 degrees Celsius. Molybdicoxide or other suitable molybdenum source is then charged to the reactorand the temperature is maintained at a temperature less than or equal toabout 120 degrees Celsius, preferably at about 70 degrees Celsius toabout 90 degrees Celsius, until the molybdenum is sufficiently reacted.Excess water is removed from the reaction mixture. Removal methodsinclude but are not limited to vacuum distillation or nitrogen strippingwhile maintaining the temperature of the reactor at a temperature lessthan or equal to about 120 degrees Celsius, preferably between about 70degrees Celsius to about 90 degrees Celsius. The temperature during thestripping process is held at a temperature less than or equal to about120 degrees Celsius to maintain the low color intensity of themolybdenum-containing composition. It is ordinarily carried out atatmospheric pressure although higher or lower pressures may be used. Thestripping step is typically carried out for a period of about 0.5 toabout 5 hours.

[0111] If desired, this product can be sulfurized by treating thisreaction mixture with a sulfur source as defined above at a suitablepressure and temperature, not to exceed about 120 degrees Celsius forthe sulfur source to react with the acidic molybdenum and basic nitrogencompounds. The sulfurization step is typically carried out for a periodof from about 0.5 to about 5 hours and preferably from about 0.5 toabout 2 hours. In some cases, removal of the polar promoter (water) fromthe reaction mixture may be desirable prior to completion of reactionwith the sulfur source. The molybdenum complex and molybdenum/sulfurcomplex produced by such method is lighter in color (when compared tocomplexes prepared at higher temperatures) while maintaining good fueleconomy, excellent oxidation inhibition, and anti-wear performancequalities. Color in this instance can be more visibly or morequantifiably using a UV spectrophotometer such as a Perkin-Elmer Lambda18 UV-Visible Double-Beam Spectrophotometer. As used herein, this testrecorded the visible spectra of molybdenum compositions at a constantconcentration in an isooctane solvent. The spectra represent theabsorbance intensity plotted versus the wavelength in nanometers. Thespectra extend from the visible region into the near infrared region ofthe electromagnetic radiation (350 nanometers to 900 nanometers). Inthis test, the highly colored samples showed increasingly higherabsorbance at increasingly higher wavelengths at a constant molybdenumconcentration. The preparation of the sample for color measurementcomprises diluting the molybdenum-containing composition with isooctaneto achieve a constant molybdenum concentration of 0.00025 g molybdenumper gram of the molybdenum-containing composition/isooctane mixture.Prior to sample measurement the spectrophotometer is referenced byscanning air versus air. The UV visible spectrum from about 350nanometers to about 900 nanometers is obtained using a one centimeterpath-length quartz cell versus an air reference. The spectra are offsetcorrected by setting the about 867 nanometer absorbance to zero. Thenthe absorbance of the sample is determined at about 350 nanometerswavelength.

[0112] Characteristics of these new molybdenum/sulfur complexes aredisclosed in U.S. patent application Ser. No. 10/159,446 filed May 31,2002, entitled REDUCED COLOR MOLYBDENUM-CONTAINING COMPOSITION AND AMETHOD OF MAKING SAME, incorporated herein by reference in its entirety.In the reaction mixture, the ratio of molybdenum compound to basicnitrogen-containing compound is not critical; however, as the amount ofmolybdenum with respect to basic nitrogen increases, the filtration ofthe product becomes more difficult. Since the molybdenum componentprobably oligomerizes, it is advantageous to add as much molybdenum ascan easily be maintained in the composition. Usually, the reactionmixture will have charged to it from about 0.01 to about 2.00 atoms ofmolybdenum per basic nitrogen atom. Preferably from about 0.3 to about1.0, and most preferably from about 0.4 to about 0.7, atoms ofmolybdenum per atom of basic nitrogen is added to the reaction mixture.

[0113] When optionally sulfurized, the sulfurized molybdenum containingcompositions may be generally characterized as a sulfur/molybdenumcomplex of a basic nitrogen dispersant compound preferably with a sulfurto molybdenum weight ratio of about (0.01 to 1.0) to 1 and morepreferably from about (0.05 to 0.5) to 1 and a nitrogen to molybdenumweight ratio of about (1 to 10) to 1 and more preferably from about (2to 5) to 1. For extremely low sulfur incorporation the sulfur tomolybdenum weight ratio can be from about (0.01 to 0.08) to 1.

[0114] The sulfurized and nonsulfurized molybdenum/nitrogen ormolybdenum/succinimide complexes employed in the present invention aretypically employed in the lubricating oil composition of the presentinvention in an amount of about 0.1 to about 1.5 weight percent, morepreferably from about 0.5 to about 1.0 weight percent.

Other Additives

[0115] The following additive components are examples of some of thecomponents that can be favorably employed in the present invention.These examples of additives are provided to illustrate the presentinvention, but they are not intended to limit it:

[0116] 1. Metal detergents: sulfurized or unsulfurized alkyl or alkenylphenates, alkyl or alkenyl aromatic sulfonates, sulfurized orunsulfurized metal salts of multi-hydroxy alkyl or alkenyl aromaticcompounds, alkyl or alkenyl hydroxy aromatic sulfonates, sulfurized orunsulfurized alkyl or alkenyl naphthenates, metal salts of alkanoicacids, metal salts of an alkyl or alkenyl multiacid, and chemical andphysical mixtures thereof.

[0117] 2. Anti-oxidants: Anti-oxidants reduce the tendency of mineraloils to deteriorate in service which deterioration is evidenced by theproducts of oxidation such as sludge and varnish-like deposits on themetal surfaces and by an increase in viscosity. Examples ofanti-oxidants useful in the present invention include, but are notlimited to, phenol type (phenolic) oxidation inhibitors, such as4,4′-methylene-bis(2,6-di-tert-butylphenol),4,4′-bis(2,6-di-tert-butylphenol),4,4′-bis(2-methyl-6-tert-butylphenol),2,2′-methylene-bis(4-methyl-6-tert-butyl-phenol),4,4′-butylidene-bis(3-methyl-6-tert-butylphenol),4,4′-isopropylidene-bis(2,6-di-tert-butylphenol),2,2′-methylene-bis(4-methyl-6-nonylphenol),2,2′-isobutylidene-bis(4,6-dimethylphenol),2,2′-methylene-bis(4-methyl-6-cyclohexylphenol),2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol,2,4-dimethyl-6-tert-butyl-phenol, 2,6-di-tert-I-dimethylamino-p-cresol,2,6-di-tert-4-(N,N′-dimethylaminomethylphenol),4,4′-thiobis(2-methyl-6-tert-butylphenol),2,2′-thiobis(4-methyl-6-tert-butylphenol),bis(3-methyl-4-hydroxy-5-tert-butylbenzyl)-su lfide, andbis(3,5-di-tert-butyl-4-hydroxybenzyl). Other types of oxidationinhibitors include metal dithiocarbamate (e.g., zinc dithiocarbamate),and methylenebis(dibutyldithiocarbamate).

[0118] 3. Anti-wear agents: As their name implies, these agents reducewear of moving metallic parts. Examples of such agents include, but arenot limited to, phosphates, phosphites, carbamates, esters, sulfurcontaining compounds, and molybdenum complexes.

[0119] 4. Rust inhibitors (Anti-rust agents)

[0120] a) Nonionic polyoxyethylene surface active agents:polyoxyethylene lauryl ether, polyoxyethylene higher alcohol ether,polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether,polyoxyethylene octyl stearyl ether, polyoxyethylene oleyl ether,polyoxyethylene sorbitol monostearate, polyoxyethylene sorbitolmono-oleate, and polyethylene glycol mono-oleate.

[0121] b) Other compounds: stearic acid and other fatty acids,dicarboxylic acids, metal soaps, fatty acid amine salts, metal salts ofheavy sulfonic acid, partial carboxylic acid ester of polyhydricalcohol, and phosphoric ester.

[0122] 5. Demulsifiers: addition product of alkylphenol and ethyleneoxide, polyoxyethylene alkyl ether, and polyoxyethylene sorbitan ester.

[0123] 6. Extreme pressure agents (EP agents): zincdialkyldithiophosphate (primary alkyl, secondary alkyl, and aryl type),sulfurized oils, diphenyl sulfide, methyl trichlorostearate, chlorinatednaphthalene, fluoroalkylpolysiloxane, and lead naphthenate.

[0124] 7. Friction modifiers: fatty alcohol, fatty acid, amine, boratedester, and other esters.

[0125] 8. Multifunctional additives: sulfurized oxymolybdenumdithiocarbamate, sulfurized oxymolybdenum organo phosphorodithioate,oxymolybdenum monoglyceride, oxymolybdenum diethylate amide,amine-molybdenum complex compound, and sulfur-containing molybdenumcomplex compound.

[0126] 9. Viscosity index improvers: polymethacrylate type polymers,ethylene-propylene copolymers, styrene-isoprene copolymers, hydratedstyrene-isoprene copolymers, polyisobutylene, and dispersant typeviscosity index improvers.

[0127] 10. Pour point depressants: polymethyl methacrylate.

[0128] 11. Foam inhibitors: alkyl methacrylate polymers and dimethylsilicone polymers.

EXAMPLES

[0129] The invention will be further illustrated by the followingexamples, which set forth particularly advantageous method embodiments.While the Examples are provided to illustrate the present invention,they are not intended to limit it. This application is intended to coverthose various changes and substitutions that may be made by thoseskilled in the art without departing from the spirit and scope of theappended claims.

Example 1

[0130] The low phosphorus lubricating oil compositions of the presentinvention were prepared by blending together at room temperature thefollowing components to obtain a SAE 0W-20 viscosity grade formulation.TABLE 1 Lubricating Oil Compositions Weight Percent of AdditiveComponent Additive Component Oil 1 Oil 2 Oil 3 Oil 4 Oil 5 Oil 6EC-Treated Ashless 5.2 5.2 5.2 5.2 5.2 5.2 Dispersant Borated-Treatedashless 3.2 3.2 3.2 3.2 3.2 3.2 Dispersant LOB Detergent 0.3 0.3 0.3 0.30.3 0.3 HOB Detergent 1.6 1.6 1.6 1.6 1.6 1.6 ZincDialkyldithiophosphate 0.7 0.7 0.7 0.7 0.7 0.7 compound^(a)Nitrogen-containing 1.5 1.5 1.5 1.5 1.5 1.5 Ashless antioxidantAlkylthiocarbamoyl 0 0 0 0.5 0.5 0.5 compound Molybdenum- 0.7 0.7 0.70.7 0.7 0.7 Succinimide Complex Base Oil: Group III 0 100 0 0 100 0 PAO(Group IV) 100 0 90 100 0 90 Ester (Group V) 0 0 10 0 0 10

[0131]^(a)0.7 weight percent in the additive package corresponds to 0.05weight percent phosphorus content based on the total weight of thelubricating oil composition.

[0132] Other additives comprise the balance of the lubricating oilcomposition.

Comparative Example A

[0133] The low phosphorus lubricating oil compositions of the presentinvention were compared with a commercially recognized long drainlubricating oil (Mobil 1®). This reference oil reference is afully-formulated synthetic passenger car engine oil formulated to SAE5W-30 viscometrics and meeting the API SJ/CF specifications. Thecompetitive commercial formulation was the minimum acceptableperformance target for the extended drain interval oils described.Duplicate reference oils were run in the below described bench tests andaverage results compared with the low phosphorus lubricating oilscompositions of the present invention.

Example 2 Rotary Bomb Oxidation Test

[0134] The Rotary Bomb Oxidation test (RBOT) was conducted according tothe standard test method specified by ASTM D 2272.

[0135] Test oil, water, and copper catalyst coil, contained in a coveredglass container, were placed in a vessel equipped with a pressure gauge.The vessel was charged with oxygen to a gauge pressure of 620 kPa (90psi, 6.2 bar), placed in a constant-temperature oil bath set at 150° C.,and rotated axially at 100 rpm at an angle of 300 from the horizontal.The number of minutes required to reach a specific drop in gaugepressure (25 psi) was the oil oxidation stability of the test sample.The longer times indicates better oxidative stability.

[0136] The precision and bias statement was generated from the researchreport (95% confidence). The data range of results in RR:D02-1409 wasfrom 30 to 1,000 minutes.

[0137] Repeatability—“The difference between successive test resultsobtained by the same operator with the same apparatus under constantoperating conditions on identical test material, would in the long run,in the normal and correct operation of the test method, exceed thefollowing values only in one case in twenty:

[0138] 0.22×

[0139] where X denotes mean value.”

[0140] Results of this test are presented in Table 2. The time to 25 psipressure drop was 100 minutes for the Reference Oil. However, the lowphosphorus lubricating oil compositions of the present invention (Oils1-6) lasted noticeably longer than the reference oil (Reference),indicating improved oxidative stability.

Example 3 Thin Film Oxygen Uptake Test

[0141] The Thin Film Oxygen Uptake test (TFOUT) was conducted accordingto the standard test method specified in ASTM D 4742.

[0142] The test oil was mixed in a glass container with three otherliquids that were used to simulate engine conditions: (1) anoxidized/nitrated fuel component, (2) a mixture of soluble metalnaphthenates (lead, copper, iron, manganese, and tin naphthenates), and(3) distilled water.

[0143] The glass container holding the oil mixture was placed in a highpressure reactor equipped with a pressure gage. The high pressurereactor was sealed, charged with oxygen to a pressure of 620 kPa (90psig), and placed in an oil bath at 160° C. at an angle of 30° from thehorizontal. The high pressure reactor was rotated axially at a speed of100 rpm forming a thin film of oil within the glass container resultingin a relatively large oil-oxygen contact area.

[0144] The pressure of the high pressure reactor was recordedcontinuously from the beginning of the test and the test was terminatedwhen a rapid decrease of the high pressure reactor pressure wasobserved. The period of time that elapses between the time when the highpressure reactor was placed in the oil bath and the time at which thepressure began to decrease rapidly was called the oxidation inductiontime and was used as a measure of the relative oil oxidation stability.The longer times indicates better oxidative stability.

[0145] The precision of this test method, as determined from statisticalexamination of interlaboratory results on oxidation point time, was asfollows:

[0146] “The difference between successive results, obtained by the sameoperator with the same apparatus under constant operating conditions onidentical test material, would in the long run, in the normal andcorrect operation of the test method, exceed the following values onlyin one case in twenty:

[0147] 0.10(x+5 min)

[0148] where x is the mean of replicate runs in min.”

[0149] Results of this test are presented in Table 2. The reference oillasts about 534 minutes prior to rapid pressure drop. Although Oil 3performed somewhat worse, Oils 1, 2, and 4-6 performed better.

Example 4 Komatsu Hot Tube Test

[0150] The Komatsu Hot Tube Test (KHTT) is used for screening andquality control of deposit formation performance for engine oils andother oils subjected to high temperatures.

[0151] A glass tube was placed inside an aluminum block and a small airhose was attached to a holder at the bottom of the glass tube. A 5-mLsyringe and 12-inch flexible tubing were filled with the oil sample. Thetubing was attached to the holder above the air hose and oil wassteadily introduced into the glass tube. Air forces the oil up the glasstube through the heating block for the duration of the test. After 16hours, the glass tubes were removed, rinsed and rated against astandard. The rating, between 0 and 10, was reported. The test was oftenrun at several temperatures to determine the deposit performance over atemperature range. Temperatures frequently tested were between 230° C.and 330° C.

[0152] Note: high numbers are desirable, a ten being a perfectly cleantube.

[0153] Results of this test are presented in Table 2. The reference oilgave an 8.5 rating versus 6.5 to 7.0 for Oils 1-6. While these resultswere lower relative to the reference oil, Oils 1-6 nevertheless yieldedvery good deposit control.

Example 5 Four-Ball Weld Test

[0154] The Four-Ball Weld Test (FBWT) was conducted according to thestandard test method specified in ASTM D 2783.

[0155] The test was operated with one steel ball under load rotatingagainst three steel balls held stationary in the form of a cradle. Testlubricant covered the lower three balls. The rotating speed was 1760rpm. The machine and test lubricant were brought to 18.33° to 35.0° C.(65° to 95° F.) and then a series of tests of 10-second duration weremade at increasing loads until welding occurred. Ten tests were madebelow the welding point. If ten loads have not been run when weldingoccurs and the scars at loads below seizure were within 5% of thecompensation line no further runs were necessary.

[0156] Results of this test are presented in Table 2. The reference oilgave a load wear index of 29.0. The low phosphorus lubricating oilcompositions of the present invention (Oil 1-6) were at least comparableand, for the oils with the supplemental antiwear/antioxidant (Oils 4-6),at least 13% better wear.

[0157] The last non-seizure load showed much the same results. That is,the lubricating oil composition of the present invention is at leastcomparable and usually superior in wear performance to the referenceoil.

[0158] These results demonstrate the wear improvement provided by thelubricating oil composition of the present invention. TABLE 2 Bench TestResults FBWT RBOT Last Non- Min. to 25 Load Wear Seizure Oil PSI DropTFOUT KHTT Index, KGF Load, KGF 1 190 796 6.5 34.4 80 2 223 683 6.5 28.663 3 179 388 7.0 28.8 63 4 180 649 6.5 32.9 63 5 177 1026 6.5 35.3 80 6159 712 7.0 35.3 80 Reference 100 534 8.5 29.0 63

[0159] It will be understood that this invention is not based on thediscovery of any one of the disclosed components as new compositions ofmatter or their individual usefulness as additive agents in lubricantoil compositions. Rather this invention is based on the discovery of alow phosphorus lubricating oil which composition useful for the severeservice function imposed by long drain life which composition comprisesa major amount of a base oil of lubricating viscosity and a minor amountof an ethylene carbonated-treated ashless dispersant, a borated-treatedashless dispersant, a high overbased metal-containing detergent, and aphosphorus-containing compound.

What is claimed is:
 1. A lubricating oil composition comprising a majoramount of a base oil of lubricating viscosity and aminor amount of eachof the following: a) from about 3.0 to about 7.0 weight percent of anethylene carbonated-treated ashless dispersant; b) from about 2.0 toabout 5.0 weight percent of a borated-treated ashless dispersant; c)from about 1.0 to about 3.0 weight percent of a high overbasedmetal-containing detergent; and d) from about 0.1 to about 2.0 weightpercent of a phosphorus-containing compound; wherein the weight percentof total phosphorus in the lubricating oil composition is no more than0.05 weight percent based on the total weight of the lubricating oilcomposition.
 2. The lubricating oil composition according to claim 1,further comprising from about 0.2 to about 6.0 weight percent of a lowoverbased metal-containing detergent.
 3. The lubricating oil compositionaccording to claim 1, further comprising from about 0.5 to about 3.0weight percent of a nitrogen-containing ashless antioxidant.
 4. Thelubricating oil composition according to claim 1, further comprisingfrom about 0.3 to about 1.0 weight percent of an alkylthiocarbamoylcompound.
 5. The lubricating oil composition according to claim 1,further comprising from about 0.1 to about 1.5 weight percent of amolybdenum/nitrogen complex.
 6. The lubricating oil compositionaccording to claim 1 wherein the base oil of lubricating viscosity isselected from the group consisting of a Group III base stock, Group IVbase stock, Group V base stock and any mixture thereof.
 7. Thelubricating oil composition according to claim 1 wherein the ashlessdispersant is selected from the group consisting of an alkenylsuccinimide, an alkenyl succinic anhydride, an alkenyl succinate ester,benzylamine or mixtures thereof.
 8. The lubricating oil compositionaccording to claim 7 wherein the ashless dispersant is an alkenylsuccinimide.
 9. The lubricating oil composition according to claim 8wherein the alkenyl succinimide is a polyalkylene succinimide.
 10. Thelubricating oil composition according to claim 9 wherein thepolyalkylene succinimide is a polyisobutylene succinimide.
 11. Thelubricating oil composition according to claim 1 wherein themetal-containing detergent is a metal phenate or metal sulfonate. 12.The lubricating oil composition according to claim 11 wherein themetal-containing detergent is a metal sulfonate.
 13. The lubricating oilcomposition according to claim 1 wherein the phosphorus-containingcompound is selected from the group consisting of metaldithiophosphates, phosphorus esters, amine phosphates and aminephosphinates, sulfur-containing phosphorus esters, phosphoramides andphosphonamides.
 14. The lubricating oil composition of claim 13 whereinthe phosphorus esters are selected from the group consisting ofphosphates, phosphonates, phosphinates, phosphine oxides, phosphites,phosphonites, phosphinites, and phosphines.
 15. The lubricating oilcomposition of claim 13 wherein the sulfur-containing phosphorus estersare selected from the group consisting of phosphoro monothionate andphosphoro dithionates.
 16. The lubricating oil composition of claim 13wherein the phosphorus-containing compound is a metal dithiophosphate.17. The lubricating oil composition of claim 16 wherein the metaldithiophosphate is a zinc dialkyldithiophosphate.
 18. The lubricatingoil composition of claim 3, wherein the nitrogen-containing ashlessantioxidant is a diphenylamine type.
 19. The lubricating oil compositionof claim 18, wherein the diphenylamine is an alkylated diphenylamine.20. The lubricating oil composition of claim 4 wherein thealkylthiocarbamoyl compound is an alkylene bis(dialkyldithiocarbamate).21. The lubricating oil composition of claim 20 wherein the alkylenebis(dialkyldithiocarbamate) is methylene bis(dialkyldithiocarbamate).22. The lubricating oil composition of claim 21 wherein the methylenebis(dialkyldithiocarbamate) is methylene bis(dibutyldithiocarbamate).23. The lubricating oil composition of claim 5 wherein themolybdenum/nitrogen complex contains a basic nitrogen-containingcompound having at least one basic nitrogen.
 24. The lubricating oilcomposition of claim 23 wherein the basic nitrogen-containing compoundemployed in the molybdenum/nitrogen complex is selected from the groupconsisting of succinimides, carboxylic acid amides, hydrocarbylmonoamines, hydrocarbon polyamines, Mannich bases, phosphoramides,thiophosphoramides, phosphonamides, dispersant viscosity indeximprovers, and mixtures thereof.
 25. The lubricating oil composition ofclaim 24 wherein the basic nitrogen-containing compound is a succinimideand the molybdenum/nitrogen-containing complex is a molybdenumsuccinimide complex.
 26. The lubricating oil composition of claim 25wherein the molybdenum succinimide complex is a sulfurized molybdenumsuccinimide complex.
 27. The lubricating oil composition of claim 25wherein the molybdenum succinimide complex is a non-sulfurizedmolybdenum succinimide complex.
 28. The lubricating oil composition ofclaim 25 wherein the molybdenum succinimide complex is employed in anamount sufficient to provide from about 10 to about 5,000 parts permillion of atomic molybdenum in the lubricating oil composition.
 29. Amethod of enhancing the life of a lubricating oil composition asevidenced by an improvement in wear, extreme pressure, oxidation, anddeposit control performance, the method comprising operating an internalcombustion engine with a lubricating oil composition comprising a majoramount of a base oil of lubricating viscosity and a minor amount of eachof the following: a) from about 3.0 to about 7.0 weight percent of anethylene carbonated-treated ashless dispersant; b) from about 2.0 toabout 5.0 weight percent of a borated-treated ashless dispersant; c)from about 1.0 to about 3.0 weight percent of a high overbasedmetal-containing detergent; and d) from about 0.1 to about 2.0 weightpercent of a phosphorus-containing compound; wherein the weight percentof total phosphorus in the lubricating oil composition is no more than0.05 weight percent based on the total weight of the lubricating oilcomposition.
 30. The method according to claim 29, further comprisingfrom about 0.2 to about 0.6 weight percent of a low overbasedmetal-containing detergent.
 31. The method according to claim 29,further comprising from about 0.5 to about 3.0 weight percent of anitrogen-containing ashless antioxidant.
 32. The method according toclaim 29, further comprising from about 0.3 to about 1.0 weight percentof an alkylthiocarbamoyl compound.
 33. The method according to claim 29,further comprising from about 0.3 to about 1.5 weight percent of amolybdenum/nitrogen complex.
 34. The method according to claim 33wherein the molybdenum/nitrogen complex is a molybdenum-succinimidecomplex.